What year is it?

13 December, 2007

In a previous post I used the term BCE without placing it in context. BCE stands for Before the Common Era (or Before the Current Era). Alongside CE (for Common Era) it is used by many historians in place of A.D. or B.C. They refer to the same dates so that A.D. 2007 is the same as 2007 CE, and Alexander the Great is thought to have died in 323 B.C. which is the same as 323 BCE.

The Anno Domini was first formulated in 525, although it did not come into common use in Europe until the 11th century. It means “In the year of our lord” and for some time after it was adopted there was debate as to whether time should be marked from the time of Jesus’ conception or from his birth. Eventually the year of his birth won out, and the estimate of when that was has given us our current basepoint for our system of years. In the 18th century many Deists who rejected the divinity of Jesus wanted to use a more secular name for the dating system since Jesus wasn’t their lord and started using CE/BCE. Since then it has become more common, although having a comic book called 2000 CE just doesn’t quite have the same ring to it…

Of course there are other calendars which take a different start date than an estimate of an ancient god’s birth. The Muslim Calendar (or Hijri Calendar) is in use in many countries around the world. Most of these countries also use the western gregorian calendar as well though, since the Hijri calendar is a lunar calendar which means that every year the months will be in a different season. This makes it difficult to plan for agriculture and so the lunar calendar is kept for marking religious observance while the solar calendar is used for working out what the season is.

The basis for the Hijri calendar is the estimated time of the Hijra, the emigration of Muhammad from Mecca to Medina. This is reckoned to have happened in 622 CE. Since the lunar calendar year used only has 354 days there have been more Hijri years since then than CE years, meaning that while 622 was 1385 solar years ago, it is currently the year 1428 AH in the Hijri calendar.

We are somewhat used to having the years already planned out for us. It’s no difficulty to have calendars extend very far into the future, in fact we rely on our understanding of time and the future to predict planetary positions which allow us, with amazing accuracy, to send robotic probes millions of kilometers to planets in our solar system where the journey time is measured in years. But in some places (such as Pakistan) the Hijri calendar cannot be extended like this, since the months are either 29 or 30 days depending on whether someone sees the lunar crescent on the 29th or 30th day of the month. If they do not see the crescent moon on the 29th day (possibly because of cloud cover!) this will mean the month will have 30 days. Forward planning can be quite tricky with such changeable dates which is why any country that uses the Hijri calendar for official business (like when to collect taxes), will tend to have predetermined the lengths of upcoming months.

Much of the history of time calculation comes from religious concerns. Trying to reckon the date of Easter for instance was a pressing problem in days gone by. But these days accurate time keeping is so necessary to our civilisation that it has become a little bit more secular than it was in the days of Umar, who gave us the start year of Hijri, or in the days of Dionysus Exiguus who gave us A.D. or even of the Roman High Priests, one of whom, Julius Caesar, gave us the Julian calendar which lasted in some parts of the world until the 20th Century. The 20th Century CE that is.